(alkylthio)alkyl mercaptans as gas odorants

ABSTRACT

A GAS ODORANT COMPRISING AN (ALKYLTHIO)ALKYL MERCAPTAN, SUITABLE AS A WARNING AGENT FOR GASEOUS HYDROCARBON FUELS. IN ONE EMBODIMENT THE (ALKYLTHIO)ALKYL MERCAPTAN ENHANCES THE EFFECT OF CONVENTIONAL ODORANT MIXTURES.

United States Patent (ALKYLTHIO)ALKYL MERCAPTANS AS GAS ODORANTS Willie W. Crouch and Ralph P. Williams, Bartlesville,

0kla., assignors to Phillips Petroleum Company No Drawing. Filed Dec. 10, 1971, Ser. No. 206,863

- e Int. Cl. Cl 3/00 US. Cl. 48197 FM 12 Claims ABSTRACT on THE DISCLOSURE A gas odorant comprising an (alkylthio)alkyl mercaptan, suitable as a warning agent for gaseous hydrocarbon fuels. In one embodiment the (alkylthio)alkyl mercaptan enhances the effect of conventional odorant mixtures.

BACKGROUND OF THE INVENTION This invention relates to malodorous chemical compounds suitable for imparting odor to gaseous hydrocarbon materials. In one of its aspects, this invention relates to odorizing hydrocarbon fuel gases. In another of its aspects, this invention relates to intensifying the odor of gas odorant agents without altering the odor type.

In one of its concepts, the invention relates to the introduction of a warning agent into gases ordinarily having no marked inherent odor by the addition of small amounts dangers. Among these odorant compounds are monomercaptans,.acyclic sulfides, cyclic sulfides and mixtures of these sulfur containing compounds. Among the compounds and mixtures known specifically as odorizers are thiophane, C H S; refinery by-product mercaptans comprising mixtures of C -C mercaptans with traces of C mercaptans present; low molecular weight mixed aliphatic sulfides-dialkyl sulfides with the same or different alkyl groups; t-butyl mercaptan; and mixtures of the groups cited above.

We have found that in addition to the sulfur containing compounds named above, (alkylthio)alkyl mercaptans are also useful alone or in combination with other malodorants, as an odorant for gases.

It is therefore an object of this invention to provide an odorant agent for gaseous hydrocarbons. It is another object of this invention to provide an agent that will enhance the odor characteristics of known gas odorant agents. It is still a further object of this invention to pro- 'vide a method for odorizing a hydrocarbon gas which ordinarily has no marked inherent odor.

SUMMARY OF THE INVENTION According to the invention an odorizing agent comprising an (alkylthio)alkyl mercaptan of the formula wherein R is an alkyl radical having 1 to 4 carbon atoms, and R is an alkylene radical having 1 to 4 carbon atoms, is added to give an odor to a gaseous material ordinarily having no marked inherent odor of its own. The gas odorant agent can be used alone or in conjunction with other known gas odorants selected from monomercaptans, acyclic sulfides, cyclic sulfides, and mixtures of these compounds. When used with other odorants (alkylthio)alkyl mercaptans intensify the odorizing characteristics of the odorants with which they are used.

Also according to this invention a process is provided for odorizing a gaseous composition which ordinarily has no marked inherent odor by incorporating in the gaseous composition a warning mixture containing an (alkylthio) alkyl mercaptan of the formula RSR'SH, wherein Ris an alkyl radical having 1 to 4 carbon atoms, and R is an alkylene radical having 1 to 4 carbon atoms. 7

The (alkylthio)alkyl mercaptan can be used in the odorization of gases such as combustible hydrocarbon gases, e.g., natural gas, propane, butane,'vap0rs and'gases recoverable in the refining of petroleum, and other gases suitable as fuels for heating, illuminating, and cooking pur oses.

In accordance with this invention, (a1kylthio)alkyl mercaptans can be used alone or in combination with other malodorants, as an odorant for gases. An (alkylthio)alkyl mercaptan has a particularly strong odor of the type most desirable as a warning agent in combustible gases having no marked inherent odor of their own. (Alkylthio)alkyl mercaptans are especially effective in intensifying the odor of commercial odorants when used in mixtures comprising such commercial odorants. As an added desirable feature, the odor of (alkylthio)alkyl mercaptans is of lower fatiguing nature than that of other known malodorants. Examples of malodorants in combination with which (alkylthio)alkyl mercaptans can be employed include lower mercaptans and sulfides such as those disclosed in US. 3,404,971. (Alkylthio)alkyl mercaptans are particularly effective for enhancing the odor level of mixtures of known odorants, particularly alkane diluted odorants, e.g., mercaptan mixtures with diluent hexane such as Scentinel C Scentinel H-25 and Scentinel H-' 70 ordorants trademarked by Phillips Petroleum Company. A mixture of 2-(ethylthio)ethyl mercaptan with Scentinel F20 gas odorant and a mixture of 2-(ethylthio)ethyl mercaptan with Scentinel E gas odorant (both trademarks of Phillips Petroleum Company) have been found to serve as especially good odorants for gaseous compositions.

Suitable (alkylthio)alkyl mercaptans, also called (alkylthio)alkanethiols, can be represented by the formula RSR'SH, wherein R is an alkyl radical having 1 to 4 carbon atoms, and R' is an alkylene radical having 1 to 4 carbon atoms. Some examples of the applicable (alkylthio)alkyl mercaptans include (methylthio)-methyl mercaptan, 2-(ethylthio)ethyl mercaptan, 2-(isopropylthio) propyl mercaptan, 3-(propylthio)-l-methylpropyl mercaptan, 2-(butylthio)butyl mercaptan, S-(tert-butylthio) propyl mercaptan, 2-(sec-butylthio)ethyl mercaptan, 2- (isobutylthio)-1,1-dimethylethyl mercaptan, Z-(methylthio)alkyl mercaptans include methylthio) methyl mercaptan, 3-(propylthio)butyl mercaptan, and the like, and mixtures thereof.

The amount of odorant which is added to the gas to be odorized can vary over a wide range but generally will be within the range of about 0.05 to 3, preferably 0.1 to 1, pounds per million cubic feet of gas. If desired, the entire amount of odorant can consist of the (alkylthio) alkyl mercaptan. However, for reasons of economy, it is presently preferred that the odorant comprise about 0.2 to 40, preferably 0.5 to 20, weight percent (alkylthio)alkyl mercaptan, the major portion of the odorant mixture being made up of odorants which are more readily available at this time.

EXAMPLE To establish the effectiveness of (alkylthio)alkyl mercaptans for intensifying the odor of commercial odorant compositions, a representative (alkylthio)alkyl mercaptan, 2-(ethylthio)ethyl mercaptan, was tested as an additive along with well known malodorous compounds in combination with a commercial odorant base. The sample combinations tested are listed below in Table I.

TABLE I Sample Commercial odorant designation base e Additive, 15 wt. percent These compositions were tested by an odor panel for type of odor and intensity of odor both on exposure and intensity of impact for a period exceeding initial perception. Data for the odor intensity test are recorded below in Table II with samples listed in order of odor intensity exposure level.

TABLE II Odor intensity e b at 0.4 lbJMM it. Odor intensity at 0.1 lb./MM Sample Exposure Impact it. exposure Intensity key: 0=nil, 1=threshold, 2=just detectable, 3=readily detectable, 4=str0ng.

b Odorants are customarily used at concentrations of 0.251.0 lb./MM cu. ft. of gas.

A difference of about 0.5 unit in odor intensity is considered significant. Thus, at a 0.4 lb./MM cubic foot concentration the odors of samples J and G were significantly greater, while samples, F, E, C, D and H exhibited about the same intensity as the unaltered controls, i.e., no odor intensification.

With regard to odor type the panel classified the odor type of samples A and B, the controls, as gaseous, i.e., the panel correctly identified the known odor type of the controls. Sample I was judged by the panel as having a gaseous type of odor characteristic of odorants presently being employed in the Southwest with the added feature of having a low fatiguing nature as compared with the other blends. Sample G was excluded from the group judged to have a gaseous type of odor. Having a gaseous odor is important only in the fact that the public has been educated to associate this odor with leaking gas and might be prone to mistake an appreciably different odor for something else.

We claim:

1. An odorized gas composition comprising a gaseous material normally having no marked odor of its own and an (alkylthio)alkyl mercaptan of the formula RSR'SH, wherein R is an alkyl radical having 1 to 4 carbon atoms, and R is an alkylene radical having 1 to 4 carbon atoms.

2. An odorized gas composition of claim 1 consisting essentially of a gaseous material normally having no marked odor of its own own and an (alkylthio) alkyl mercaptan of the formula RSR'SH, wherein R is an alkyl radical having 1 to 4 carbon atoms, and R is an alkylene radical having 1 to 4 carbon atoms.

3. An odorized gas composition of claim 2 wherein the (alkylthio)alkyl mercaptan is 2-(ethylthio)ethyl mercaptan.

4. A gas odorant agent wherein said agent consists essentially of a mixture of an (alkylthio)alky1 mercaptan of the formula RSR'SH, wherein R is an alkyl radical having 1 to 4 carbon atoms, and R is an alkylene radical having 1 to 4 carbon atoms, and a gas odorant consisting essentially of gas odorants selected from the group consisting of mercaptans, acyclic sulfides, cyclic sulfides, and mixtures thereof, and an alkane diluent.

5. A gas odorant agent of claim 4 wherein the (alkylthio alkyl mercaptan is 2- ethylthio ethyl mercaptan.

6. A gas odorant agent of claim 4 consisting essentially of a mixture of an (alkylthio)alkyl mercaptan of the formula RSR'SH, wherein R is an alkyl radical having 1 to 4 carbon atoms, and R is an alkylene radical having 1 to 4 carbon atoms, and a gas odorant consisting essentially of gas odorants selected from the group consisting of monomercaptans, acyclic sulfides, cyclic sulfides, and mixtures thereof.

7. A gas odorant agent of claim 6 wherein the (alkylthio)alkyl mercaptan is 2-(ethylthio)ethyl mercaptan.

8. A gas odorant of claim 6 wherein the (alkylthio) alkyl mercaptan comprises from about 0.2 to about 40 weight percent of the total mixture.

9. A process for odorizing a gas comprising incorporating in said gas from about 0.05 to about 3 pounds per one million cubic feet of said gas of a warning mixture comprising an (alkylthio)alkyl mercaptan of the formula RSR'SH, wherein R is an alkyl radical having 1 to 4 carbon atoms, and R' is an alkylene radical having 1 to 4 carbon atoms.

10. The process of claim 9 wherein said warning mixture consists essentially of an (alkylthio)alkyl mercaptan of the formula RSR'SH, wherein R is an alkyl radical having 1 to 4 carbon atoms, and R is an alkylene radical having 1 to 4 carbon atoms.

11. A process for odorizing a gas comprising incorporating in said gas from about 0.05 to about 3 pounds per one million cubic feet of said gas of a warning mixture consisting essentially of the odorant of claim 4.

12. A process for odorizing a gas comprising incorporating in said gas from about 0.05 to about 3 pounds per one million cubic feet of said gas of a warning mixture consisting essentially of the odorant of claim 6.

References Cited UNITED STATES PATENTS 2/1959 Eaton et a1. 48-495 10/1968 Olund 48195 U.S. Cl. X.R. 48l95; 252-408 

